C3 Distributor Tach Gear

[Kevin Morris]

Hello all. Has anyone ever removed/replaced a "cross gear" (the gear driving the tach off of the distributor, on a car with a mechanical tach drive)? Some questions:

1) Once the tach cable is removed from the distributor shaft housing, there is a coupler that must be removed. Apparently, it takes a very wide screwdriver, or some sort of special tool to remove this coupler? I am assuming it just screws out?

2) Once this coupler is removed, can the cross gear (tach gear inside the distributor shaft housing) be removed through the coupler hole? Or must the entire distributor be removed?

3) Once the gear and coupler are replaced with new pieces, are there any engine timing issues to be addressed?

Thx,
Kevin #39927

[Clem Z.]

Re: C3 Distributor Tach Gear

if the cross gear is bad most likely the distributor shaft gear will be also so you need to replace it and do this you must remove the distributor from the engine. also the broken pieces should be removed from the inside of the distributor housing. some times the problem is caused by the cross gear binding up in the bronze housing and this must be corrected also

[Kevin Morris]

Re: C3 Distributor Tach Gear

Clem, I understand that the gear on the distributor shaft may be part of the cause, as well. I am simply trying to take one step at a time. The tach worked perfectly, until I removed the cable to do some engine cleaning/detailing. When I hooked the cable back up, the tach needle either "floats around" or does not work at all. It may be the cable, too. I have a new cable, but would like to remove the brass (it is actually brass, not bronze) coupler and the tach gear to inspect, being going any further (i.e. removing the entire distributor). Again, does the brass coupler simply screw out? And, can the tach gear be removed through that same hole, left by the removal of the coupler?

[Joe L.]

Re: C3 Distributor Tach Gear

Kevin-----

The coupler is threaded and screws into the distributor body. You can remove it using a wide-blade tool. Some of the vendors sell a simple tool, but you can improvise. It should be a piece of metal that fits tightly in the slot and with enough of an "arm" for you to get enought leverage to screw it out. Sometimes, these can be a bit stubborn.

Once the coupler is out the gear can be easily removed. Usually, it will come out with the coupler, but if it doesn't, just reach down, and with your fingers, pull it out.

If the gear is completely intact and, apparently, in good shape, then it's VERY unlikley that it's the cause of your problem. You'll then need to look elsewhere. However, if the gear is "chipped" or has a "chunk" out of it, then it must be replaced. In this case, as clem mentioned, you need to replace both the mainshaft and the cross gear.

[Jim T.]

Re: C3 Distributor Tach Gear

Kevin a tool I use to remove the coupler is a good gasket scraper type tool. In a previous post Joe Lucia mentions a lubricant to use on the distributor tach gear. This should be regular maint for the tach gear.

[Patrick H.]

Re: C3 Distributor Tach Gear

In addition, if you need to replace the mainshaft, you will either need to 1) find an exact match distributor to swap shafts, or 2) purchase a new mainshaft, and have the distributor recurved to match your original specs.

I've done both options. I can tell you from experience that the current reproduction mainshafts do NOT have an autocam on the top of them that resembles much of anything. It WILL have to be recurved.

But, as Joe noted, if your cross gear is in great shape, then your distributor is not the problem. Consider lubricating your tach cable and see if that helps. If not, you will have to replace it. And, amazingly enough, the current Delco cable is too long for a good fit. So, you wil either have to live with a poor fit, or get your current cable repaired.

Have fun.

Patrick

[Harmon C.]

Re: C3 Distributor Tach Gear

Kevin Their are other parts that can be bad. The shaft is the most money and replace if it is bad but check it . The brass housing can be worn egg shaped. The cross shaft gear can be bad on the gear end or where the cable fits in. Some years have a button. The cable can get worn short and slip in the cross shaft. If money is no object replace it all as a mix of old and new parts can spell trouble if you miss something. Otherwise check your parts for damage and replace only those that are bad. Lyle

[Joe L.]

Re: C3 Distributor Tach Gear

Patrick-----

You can also have the "auto-cam" from the top of the old mainshaft removed and re-brazed to the top of the new shaft. This is what I recommend to retain original mechanical advance characteristics. Among others, Hi-Tech Innovations of Florida does this service.

[Patrick H.]

Re: C3 Distributor Tach Gear

Joe,

That would likely be the best option, if in fact Hi-Tech does this. I couldn't find anyone else who would do that for me.

If it ends up being the tach, he may be best off sending them the whole unit for a re-do.

Patrick

[Joe L.]

Re: C3 Distributor Tach Gear

Patrick-----

As far as I know, Hi-Tech still performs this service. I learned at Carlisle that Jim Dwyer, the original owner of Hi-Tech, passed away a few years ago. I was saddened to learn that since I knew Jim and he was a great guy to talk to. Anyway, his son still runs the business and I think that he is the "manufacturing guy" that actually does all the work.

They don't work on any tachometer instruments, though.

[Patrick H.]

Re: C3 Distributor Tach Gear

Yes, I meant distributor.

See what I get for trying to quick type up a reply between patients?

Patrick

[Joe L.]

Re: C3 Distributor Tach Gear

Patrick-----

I hope that Jim Dwyer wasn't one of your patients!

[Patrick H.]

Re: C3 Distributor Tach Gear

Nope. Michigan is nowhere near Florida.

Would have been nice, though, as I would have liked watch him restore distributors.

Patrick